The present invention relates to an optically pumped solid-state laser oscillator.
A solid-state laser oscillator using, for example, Nd:YAG (Neodymium:Yttrium Aluminium Garnet;Y.sub.3 Al.sub.5 O.sub.2) is excited by a light having a strength within a range of photo absorption band of the Nd:YAG crystal, such as a light emitted from a xenon lamp. Fluorescent light emitted from the crystal is resonated by a photo resonator, thereby taking place the laser oscillation. Recently, due to the increase of the output from a semiconductor laser device, it has become possible to effectively take out a laser beam while using an excitation light having a wavelength in the range of from 806 to 811 nm which fall within a range of an absorption wavelength of the crystal of the Nd:YAG laser.
However, as shown in FIG. 3 representing a relation between a wavelength of an excitation light and a light output, the Nd:YAG crystal which is easily accessible and frequently used is narrow in the absorption wavelength range, i,e, from 806 to 811 nm, and besides the commonly used high output semiconductor laser sources vary in wavelength depending upon the change of the environmental temperature by about 0.25 nm/deg. at an average, as evidenced in the graph shown in FIG. 4 representing a relation between a casing temperature and an oscillation wavelength. Therefore, in order to ensure the use of the solid-state laser oscillator under operating temperatures, it has been necessary that temperature compensation be carried out by a temperature control mechanism using, for example, a Peltier element. Although a Nd:YVO.sub.4 or a Nd:BeL has been known as a solid-state laser substance which has a wider absorption band, such substances are not commonly used and hence expensive in cost.